At my mom's home, her sewer line is 250 feet 4" clay pipe.
She has two 1.6 bowls and one 3.5
The 3.5 has much slower drainline carry than the 1.6 bowls.
That line has been there since 1962 and the only time we snaked it was when paper caught on a gas line that had been drilled through the clay pipe.
We cut the pipe with the cutters on the snake and had the gas company out to relocate the gas line. It's been fine ever since.
Warning: Cutting a gas line inside a sewer line can have serious problems.